[LUM#5] Exploring the Universe
December 2013: The Sun gains a new satellite. The newest addition is named Gaia. Its mission: to explore a galaxy that is as close to us as it is little known—our own. And to help us better understand the universe…
50 billion data points: that’s what the European Gaia satellite—an explorer of the far reaches of our galaxy—sends us every day. It took no less than three years to begin deciphering this enormous amount of information, using complex software, some of which was developed by the Montpellier Laboratory for Universe and Particles (LUPM). Your computer, on the other hand, would have taken hundreds of years to complete this task…
Mapping the Galaxy
Comfortably positioned aroundthe “Lagrange point”1.5 million kilometers away—the precise location in the Sun-Earth system where the gravitational forces of the two bodies balance each other out—Gaia observes, catalogs, and calculates. And it’s helping us make giant leaps forward in our understanding of the Milky Way. This is because most of the objects observed by the satellite were previously poorly understood:“Gaia has collected data on 1.15 billion stars. That’s enormous! Until now, we only knew the distances to about 100,000 stars,” enthuses Gérard Jasniewicz, an astronomer at LUPM.
The primary objective of the Gaia mission is to measure the positions, distances, and movements of celestial objects within the galaxy. The stakes are high:“The goal is to create the most accurate three-dimensional map ever produced—and thereby to understand the very structure of our galaxy,” explains Fabrice Martins, also an astronomer at LUPM.
A galaxy that remains largely unknown. Why? First of all, because it is enormous. Want an idea of its size? If we could travel at the speed of light, it would take us about 100,000 years to cross it from one end to the other…“With Gaia, we’ll be able to accurately map all the bright stars in our galaxy located within 30,000 light-years,”explains Gérard Jasniewicz.
Time Machine
One reason we know so little about the Milky Way is that we are part of it.“It’s paradoxical: in some respects, we know less about the Milky Way than we do about certain other galaxies,” Fabrice Martins continues. “We lack the necessary perspective to form a comprehensive picture of it. Many stars are hidden from us by clouds of gas and dust that form a curtain impenetrable to telescopes.”
The brightness, position, and speed of stars: the European satellite and its many instruments (see sidebar) have much to teach us based on this fundamental data. In this vast undertaking, the task assigned to the LUPM is crucial: to study the “radial velocities” of stars—how fast they are moving toward or away from us.“Gaia will also reveal the intrinsic brightness of stars, and thus their mass: these are key data for characterizing them,” continues Fabrice Martins.
A way to better understand these brilliant populations—blue, white, yellow, orange, and red stars, as well as dwarfs, giants, and supergiants—that inhabit our galaxy. Many researchers at LUPM, who are working on star classification, are eagerly awaiting these results, which will allow them to test hypotheses, models, and theories. They are not alone. Gaia is a source of inspiration for the global scientific community, which will have free access to all the project’s data. And which hopes to see new horizons open up soon in many disciplines…
New Horizons
Gaia is not only an explorer and cartographer of our galaxy, but also its archaeologist. The speeds, movements, ages, and chemical compositions of stars—all of these elements provide valuable insights into the galaxy’s past and how it formed.“A telescope is a time machine!” sums up Gérard Jasniewicz.
By the end of its mission—which is scheduled to last until 2020 but may well be extended—the Gaia satellite will have advanced our knowledge across the board, opening our eyes to a wide range of topics: quasars, exoplanets, asteroids, other galaxies… This galactic encyclopedia will even make it possible to verify the effects of universal gravity on a very large scale—and thus to test even the fundamental laws of physics. It is such a vast encyclopedia that scientists are already looking forward to the wealth of research topics it offers… which will simply be waiting to be explored.
"Revolutionary"
The Gaia project is about“mapping more objects, with greater precision and over greater distances,” the scientists summarize. A “revolutionary” satellite that observes 50 million stars every day.
Equipped with two telescopes, this technological marvel also features 106 sensors—the equivalent of a camera with a resolution of one billion pixels. 450 scientists from 25 European countries are working on this project led bythe ESA (European Space Agency).
Check out theUM podcasts, now available on your favorite platform (Spotify, Deezer, Apple Podcasts, Amazon Music, etc.).